The present invention relates to a laser apparatus, particularly to a laser apparatus emitting and receiving a plurality of laser beams of different wavelengths and its applications.
Laser beams are widely used in various industries such as optical communications. For instance, U.S. Pat. No. 6,061,319 and Japanese Patent Laid-Open No. 11-183324 disclose laser apparatuses comprising switching means. Particularly, U.S. Pat. No. 6,061,319 discloses a fiber laser apparatus for use in optical communications comprising wavelength-selecting means having a plurality of oscillating wavelengths with wavelength difference of 100 GHz (0.8 nm) in a 1.5-xcexcm band. Also, Japanese Patent Laid-Open No. 11-183324 discloses an optical switch for switching the ON/OFF of a plurality of laser beam sources and measuring paths. However, there is room for improvement in them in terms of reliability, operability and miniaturization.
Also known as measurement apparatuses utilizing laser beams are microscopes such as a scanning-type, confocal microscope. This scanning-type, confocal microscope is an apparatus irradiating a laser beam to an object to be measured, and observing a fluorescent beam emitted from the object. Because the scanning-type, confocal microscope can focus on a much narrower region than usual microscopes, it can selectively observe a portion having a particular thickness in a stereoscopic sample. This confocal microscope is used, for instance, in the quantitative observation of the locality of proteins in cells as basic data for genetic information. In this measurement, fluorescent labels are given to several types of proteins having different molecular structures. Because fluorescent labels absorb light beams of particular wavelengths, exciting light beams should be present in the same number as that of the fluorescent labels.
Laser beams used for exciting beams range from ultraviolet to red. The details of a scanning-type, confocal microscope using laser beams are described in Japanese Patent Laid-Open No. 6-214162. Further, Japanese Patent Laid-Open Nos. 9-243598, 11-127900 and 11-243997 disclose DNA sequencers and DNA chip examination apparatuses as laser-applied apparatuses.
In the identification of proteins using a confocal microscope according to the above conventional procedures, there have been problems as described below in the course of measurement. That is, the conventional measurement procedures require that exciting light sources be switched in the observation from a certain protein to a next protein. Specifically, after a laser beam source is disconnected from a microscope, another laser beam source of a different wavelength is connected to the microscope. Such troublesome disconnecting and connecting operations of laser beam sources and a microscope are required whenever objects to be measured are changed, posing problems that an operator may be exposed directly to laser beams. Further, because an operator frequently disconnect a connector having fiber ends exposed mechanically from the apparatus, the fiber ends are likely to be damaged, resulting in trouble and deterioration of performance. In addition, the damage of the fiber ends is difficult to find by the naked eye, leading to deterioration in reliability and reproducibility of data.
In view of such problems, laser apparatuses designed to eliminate such troublesome changing operations and to avoid dangerous operations were devised and put into practical use. This apparatus is schematically shown in FIG. 8. This apparatus comprises an optical Table 70, and three laser beam sources 72-1, 72-2, 72-3 of different wavelengths arranged as shown in FIG. 8, wherein laser beams emitted from laser beam sources 72-1, 72-2, 72-3 are guided to focusing lenses 78-1, 78-2 in a focusing system 75 by mirrors 76-1, 76-2, 76-3, and supplied to a laser-applied apparatus 19 via an optical fiber 17. Because each mirror 76-1, 76-2, 76-3 has a wavelength selectivity that reflects a laser beam of a wavelength emitted from the corresponding laser beam source 72-1, 72-2, 72-3 while permitting laser beams of other wavelengths to pass through, laser beams of different wavelengths can properly be selected without carried out the above-described switching operations. In with this constitution, a light path from a laser beam source 72 to a focusing lens 78 is the air (air-waveguide system).
However, in this conventional apparatus, optical parts such as the optical table 70 and the mirrors 76 may be elongated, deformed or displaced from their original positions due to change in the ambient temperature and heat generated from the laser beam sources 72, resulting in change in the light paths as shown by the dotted lines in FIG. 8. As a result, coupling decreases between the laser beam sources 72 and the optical fiber 17, failing to provide laser beams necessary for the laser-applied apparatus 19 such as a microscope, and thus failing to expect normal operations of the laser-applied apparatus.
In addition, because a plurality of laser beam sources 72 are mounted two-dimensionally onto the optical table 70, a rather wide optical table is needed, resulting in difficulty in disposing it in a proper narrow place. For instance, in the case of mounting three or four laser beam sources onto an optical table, an optical table as wide as up to 1 m2 is needed in the conventional technologies. Further, because of the air-waveguide system, a structure for shielding the light path and its surrounding should be added to ensure safety. Thus, the conventional laser apparatus per se is large and not easy to handle.
Accordingly, an object of the present invention is to solve the problems of the prior art technologies by changing a waveguide system from the air-waveguide system to an optical fiber-waveguide system.
The laser apparatus according to the present invention has a structure in which a laser beam emitted from each laser beam source is led to a switching and coupling means via an input optical fiber, and one of a plurality of input optical fibers is arbitrarily selected such that a desired laser beam is supplied to a laser-applied apparatus.
The switching and coupling means has a structure in which the desired one of a plurality of optical fibers can be selected, and which input optical fibers and output optical fibers are positioned with such high accuracy that loss at coupling can be suppressed as much as possible. Also, with a control circuit connected to the switching and coupling means, the ON/OFF time and sequence can be controlled according to the predetermined program, thereby providing a laser apparatus with more diversified functions and applicability. Particularly in the biomedical applications, a plurality of laser beams of 30 nm or more in wavelength difference can be switched by the switching and coupling means, thereby eliminating troublesome and dangerous operations and thus improving reliability and operability with further miniaturization.
The laser apparatus for selectively supplying a plurality of laser beams of 30 nm or more in wavelength difference to a measuring apparatus according to the present invention comprises optical fibers through which the laser beams pass, and a switching and coupling means connected to the optical fibers for selecting at least one laser beam from a plurality of laser beams. The laser beams preferably have a wavelength of 350-800 nm.
The switching and coupling means preferably has at least a function to turn off said laser beams. A plurality of switching and coupling means preferably are connected in series or in parallel.
In a preferred embodiment of the present invention, the laser apparatus for selectively supplying a plurality of laser beams of 30 nm or more in wavelength difference to a measuring apparatus comprises a plurality of laser beam sources for emitting laser beams having different wavelengths; a plurality of input optical fibers each connected to the laser beam source, through which the laser beams pass; at least one switching and coupling means having a plurality of inputs connected to the input optical fibers and at least one output for selecting at least one laser beam from a plurality of the laser beams; at least one output optical fiber connected to the output of the switching and coupling means; and a measuring apparatus connected to the output optical fiber.
In another embodiment of the present invention, the switching and coupling means comprises input terminals connected to the input optical fibers together with at least one NULL terminal not connected to the input optical fiber, the terminals being arranged in parallel at an equal interval, wherein the output optical fiber is slidable transversely relative to the parallel arrangement of the terminals, such that the output optical fiber is connected to one of the terminals.
The laser-applied apparatus according to the present invention comprises the above laser apparatus, and a fluorescent microscope.
The laser-applied apparatus preferably comprises the above laser apparatus, and a DNA sequencer. The laser-applied apparatus preferably comprises the above laser apparatus, and an examination apparatus connected to the laser apparatus. The examination apparatus is preferably a DNA chip examination apparatus, protein examination apparatus or a DNA probe array examination apparatus.
In the method for using the above laser apparatus according to the present invention, laser beams supplied from the laser apparatus are introduced into at least two types of laser-applied apparatuses.
The accurate positioning of a plurality of input optical fibers in parallel at an equal interval and the position control of output optical fibers by sliding can be achieved by applying technologies developed in the technical field of optical communications or combining them with conventional technologies.
Further, with a NULL terminal capable of keeping an OFF state added to the switching and coupling means, troubles at the time of switching can be prevented. That is, the NULL terminal can prevent unnecessary light beams from being transmitted to the laser-applied apparatus at the time of switching the optical fibers, thus extremely effective as a means for suppressing strayed laser beams. Thus, the reliability of the measured data is further improved. Also with this NULL terminal, the ON/OFF control of laser beams is easily conducted, making it possible to control the irradiation time of laser beams accurately.